Filter device

ABSTRACT

A filter device for filtering fluids, such as fuels, including diesel fuel, comprising a filter housing ( 1 ), inside which a filter element ( 17 ) can be fastened in an exchangeable manner, which filter element has a filter medium that surrounds an inner filter cavity ( 25 ), a fluid inlet ( 21 ) leading to the unfiltered side ( 27 ) of the filter element ( 17 ), a fluid outlet ( 9 ) for the outflow of filtered fluid from the filtered side ( 25 ), and a tank return connection ( 13 ), is characterized in that an equalizing tube ( 49 ) is provided extending in the filter housing ( 1 ) up to a maximum filling level height provided for the filtration operation, which equalizing tube is connected at its bottom end to the tank return connection ( 13 ) and is open at its top end ( 51 ), and in that the tube ( 49 ) has, at a point located at a distance from the top and bottom end of the tube, an inner control part ( 60 ), in which a through-hole ( 61 ) is located, which forms a throttle point.

The invention relates to a filter device for filtering fluids, such as fuels, including diesel fuel, comprising a filter housing, inside which a filter element can be fastened in an exchangeable manner, which filter element has a filter medium that surrounds an inner filter cavity, a fluid inlet leading to the unfiltered side of the filter element, a fluid outlet for the outflow of filtered fluid from the filtered side, and a tank return connection. The invention further relates to a filter element intended for use in such a filter device.

Filter devices of the type described above are state of the art. They are used, for example, in fuel systems for internal combustion engines to protect sensitive components, in particular injection systems, from damage caused by pollutants carried in the fuel, such as dirt particles or water content that is to be separated at the filter element. High standards must be demanded with regards to the reliable functioning of such filter devices because the operation of such systems with a non-operable filter device would lead to significant economic losses due to the malfunctions or damage to injection systems that it would cause.

Given these problems, the objective of the invention is to provide a filter device with particularly reliable operating behavior.

In accordance with the invention, this problem is solved by means of a filter device having the features of claim 1 in its entirety.

In accordance with the characterizing portion of claim 1, a significant special feature of the invention is that an equalizing tube is provided in the filter housing, which equalizing tube extends from its bottom end connected to the tank return connection up to a maximum filling level height provided for the filtration operation, with the tube being open at its top end and having, at a point located at a distance from the top and bottom end of the tube, an inner control part, in which a passage opening is located, which forms a throttle point. When the size of the passage opening, in particular in the form of a through-hole, which is located in the control part, is appropriately selected, a pressure-relieving ventilation of the filter housing in the direction of the tank return is produced by means of the equalizing tube, while at the same time the desired feed pressure is maintained due to the throttling effect in normal operation. A safety device is thus created which both prevents breakdowns caused by poor housing ventilation and which can also relieve pressure in the filter housing via the throttle point.

The control part, which forms a kind of closure part, is preferably disposed in the central longitudinal area or in the vicinity of this longitudinal area of the tube.

In preferred exemplary embodiments, in which the filter element can be fastened via at least one end cap on an element seat of the filter housing, the equalizing tube is mounted on the filter housing inside the element seat and extends coaxial to the longitudinal axis of the filter element located in the functional position through the end cap thereof fastened to the filter seat and through the filter cavity. Such an arrangement of the equalizing tube concentric to the longitudinal axis results in a particularly compact construction of the filter device.

In advantageous exemplary embodiments, the external diameter and the internal diameter of the tube can have a stepped design, with the tube abutting the element seat by means of the longitudinal section of the larger external diameter and of the larger internal diameter, and the control part comprising the through-hole forming the transition between the larger internal diameter and the smaller internal diameter of the tube.

The top end cap of the filter element may particularly advantageously have a tube connection projecting into the inner filter cavity, through which the top end area of the tube extends in the functional position of the filter element.

The arrangement can particularly advantageously be such that sealing packing is provided inside the tube connection of the top end cap, which sealing packing is penetrated in the functional position by the tube and forms a sealing connection with said tube, which sealing connection seals the inner filter cavity relative to the housing inner side. In a filter device, in which the filter element is flowed through in the filtration operation from its outside to the filter cavity forming the filtered side, the seal between the unfiltered side on the housing inner side and the filtered side is automatically created when the filter element is placed in the functional position.

In particularly advantageous exemplary embodiments, a fluid path leading from the unfiltered side to the tank return connection and a blocking device are provided in the filter housing, which blocking device blocks this fluid path when a filter element is inserted into the housing and unblocks this fluid path when the filter element is removed. A bypass is thus formed as an additional safety device in the feed line, which leads from a respective tank via a feed pump and the filter housing to the consumer (such as an injection system), which bypass is closed by means of the blocking device as a function of the presence of a filter element inserted into the filter housing, but is automatically opened in the absence of the filter element. The absence of a filter element and the thus effected opening of the bypass via the tank return connection to the non-pressurized tank leads to an interruption of the feed flow to the consumer, which eliminates the risk of operation taking place when the filter element has inadvertently not been inserted into the filter housing. With regards to the design of the blocking device, the arrangement can particularly advantageously be such that the blocking device has an annular body, which projects at the bottom end cap of the filter element and surrounds on this end cap the outlet aperture from the filter cavity forming the filtered side, with the annular body engaging in a sealing manner in an annular gap when the filter element is inserted, which annular gap is formed on the element seat of the housing and is in fluid connection with the tank return connection.

In particularly preferred exemplary embodiments, a barrier device can be formed as an additional safety device in the filter housing between the fluid outlet and the filtered side of the filter element, which barrier device allows an influx of fluid to the fluid outlet only upon reaching a predetermined filling level in the housing by means of overflowing of the barrier device. This eliminates the risk that, in the absence of a filter element and in spite of the thus opened bypass, fuel supplied to the housing via the fluid inlet can reach the fluid outlet, because the barrier device can be overflowed only when a predetermined filling level height is reached, while such a filling level cannot be reached when the bypass is opened, even if fuel is still being supplied.

The barrier device can particularly advantageously have a tubular body, which projects from the element seat into the inner filter cavity of the inserted filter element up to the predetermined filling level height and is connected inside the element seat to the fluid outlet.

The subject matter of the invention is also a filter element intended for use in a filter device according to one of claims 1 through 12, which filter element has the features of claim 13.

The invention is explained in detail below with reference to an exemplary embodiment depicted in the drawings, in which:

FIG. 1 shows a perspective oblique view of the exemplary embodiment of the filter device, depicted cut-open and partially broken away, with a filter element inserted into the filter housing and

FIG. 2 similarly shows a perspective oblique view of the exemplary embodiment, depicted cut-open and partially broken away, without a filter element in the filter housing.

The invention is explained below using the example of a fuel filter, which is provided in a fuel supply system (not shown) of an internal combustion engine for the cleaning of diesel oil. The invention is also suitable for other fluids as well as for other applications.

The device has a filter housing 1 in the form of a hollow cylindrical pot, which can be closed in a tight manner at its top open end by means of a removable screw-on lid 3 with the assistance of a sealing element 5. The housing 1 has a bottom part 7, which is closed as far as housing connections, which are not visible in the figures. Said housing connections are an outlet connection for the discharge of cleaned diesel oil and a tank return connection. The outlet connection is connected to an outlet chamber 11, and the tank return connection is in fluid connection with a return chamber 13, which are formed in the bottom part 7 in that area which forms an element seat 15, in which a filter element 17 inserted into the housing 1 can be fastened by means of its bottom end cap 19, which filter element is depicted in the installed state in FIG. 1.

During operation, diesel oil is conveyed inside the not depicted fuel supply system by means of a feed pump from a tank to the fluid inlet of the filter housing 1. The fluid inlet not visible in the drawings is located on the housing 1 above the bottom part 7 and approximately at half the height of the filter housing. The inflowing fuel flows through the inserted filter element 17 from the outer unfiltered side 27 from the outside inwards to an inner filter cavity 25, which forms the filtered side in the filtration operation. As can be seen from FIG. 1, the bottom end cap 19 of the filter element 17 in the figure has an axially projecting annular body 31 which is coaxial to the central opening 29 of the inner filter cavity 25, which annular body surrounds the opening 29 at a radial distance and forms, in cooperation with the element seat 15, a blocking device. For this purpose, the element seat 15 forms an annular gap 33 forming the inlet part of the return chamber 13, which annular gap is delimited on the outside by a tube connection 35 projecting from the element seat 15 and on the inside by an annular rib 37 which has a somewhat smaller projection. A sealing element 39 lying radially on the outside of the annular body 31 forms a seal on the outer side of the annular gap 33, while a sealing element 41 forms a seal on the inner side of the annular rib 37.

The remaining design features of the element seat 15 are clearly evident in FIG. 2. A tubular body 43 serving as a barrier device extends from the element seat 15 concentric to the longitudinal axis of the device through the passage 29 of the end cap 19 axially into the inner filter cavity 25 of the filter element 17 inserted into the housing 1. The end cap 19 has a tube piece 32 surrounding the passage 29, which extends axially upwards and forms a bearing surface for the bottom end of the fluid-penetrable support tube 34 of the filter element 17. A sealing element 36 forms on the tube piece 32 a seal of the passage 29 relative to the outer side of the tubular body 43. Said tubular body is open to the outlet chamber 11 as can be seen in FIG. 1. By means of the top open tube end 47, the tubular body 43 opens at approximately half the height of the filter housing 1 in the inner filter cavity 25 of the inserted filter element 17, i.e. the filtered side in the filtration operation. Thus, when there is a normal filling level in a filtration operation with an inserted filter element 17, the fuel flowing through the filter element 17 from the outside to the inside overflows the tube end 47 of the tubular body 43, so that cleaned fuel flows into the outlet chamber 11 and exits the filter housing 1 via the fluid outlet connection (not shown).

If, as is shown in FIG. 2, no filter element 17 is located in the housing 1 and thus no blocking device is acting in the annular gap 33 because the annular gap 33 is open to the return chamber 13 and thus to the tank return, no filling level of fuel can be built up in the housing 1 that could overflow the tube end 47 of the tubular body 43 serving as a barrier device. If the device were operated without an inserted filter element 17, supplied fuel overflowing the tube connection 35 would flow away to the tank via the annular gap 33 and the return chamber 13, so that no unfiltered fuel could reach the fluid outlet connection via the outlet chamber 11. Because the annular gap 33 is delimited by the tube connection 35 projecting from the bottom part 7, which must be overflowed, a residual sump remains in this case inside a collection chamber formed on the bottom of the housing 1, in which pollutants that may fall from the outer side of the filter element 17 when it is removed are held and do not return to the tank via the return.

Inside the tubular body 43, an equalizing tube 49 extends from the element seat 15 concentrically to the longitudinal axis through the inner filter cavity 25 of the inserted filter element 17 and so far upwards that its top end 51 lies at the maximum filling level height provided for the filtration operation. The equalizing tube 49 penetrates an opening 52 located on the top end cap 53 of the inserted filter element. This opening is formed by the inner side of a tube connection 71, which extends from the top end cap 53 of the filter element 17 axially downwards into the filter cavity 25. The inner side of the tube connection 71 has an annular rib 72 projecting radially inwards, by means of which an elastomer sealing packing 55 is fixed. When the filter element 17 is in the functional position, the equalizing tube 49 penetrates the sealing packing 55 by means of its top end area which is tapered towards the end 51 and thus forms the seal between the top end of the filter cavity 25 and the housing inner side, i.e., the seal between the filtered side and the unfiltered side 27 located on the outer side of the filter element 17.

While the equalizing tube 49 is open at its top end 51, the bottom end of the equalizing tube 49 is closed up to a channel 57 running transverse to the longitudinal axis, which connects the inside of the equalizing tube 49 to the return chamber 13. As can be seen from the figures, the equalizing tube 49 is stepped both in its external diameter and in its internal diameter, with the bottom area 70 abutting the element seat 15 having a smaller internal diameter than the area 78 above it, and the external diameter of the equalizing tube 49 also being different over most of the length of these areas 68, 70, i.e. being smaller in the top part than in the bottom part. At the transition point between the area 68 of smaller internal diameter and the area 70 of larger internal diameter, a type of control or closing part 60 is located in the tube interior, through which part a passage opening, in particular in the form of a through-hole 61, extends. The control part 60 with the through-hole 61 is located in the central longitudinal area of the equalizing tube 49, more specifically, a little below the center of the tube length. The through-hole 61 is dimensioned such that it forms a throttle point, by means of which the interior of the filter housing 1, which forms the unfiltered side 27 in the filtration operation, is connected to the tank return connection. The size of the through-hole 61 is selected such that, while a pressure-relieving, automatically acting ventilation device for the filter housing 1 is created by means of the equalizing tube 49, a desired predetermined feed pressure is nevertheless maintained in normal filtration operation due to the throttling effect of the through-hole 61. Because the throttle point 61 is disposed approximately centrally inside the equalizing tube 49, the flow conditions are improved due to an optimized throttling effect. 

1. A filter device for filtering fluids, such as fuels, including diesel fuel, comprising a filter housing (1), inside which a filter element (17) can be fastened in an exchangeable manner, which filter element has a filter medium that surrounds an inner filter cavity (25), a fluid inlet (21) leading to the unfiltered side (27) of the filter element (17), a fluid outlet (9) for the outflow of filtered fluid from the filtered side (25), and a tank return connection (13), characterized in that an equalizing tube (49) is provided extending in the filter housing (1) up to a maximum filling level height provided for the filtration operation, which equalizing tube is connected at its bottom end to the tank return connection (13) and is open at its top end (51), and in that the tube (49) has, at a point located at a distance from the top and bottom end of the tube, an inner control part (60), in which a through-hole (61) is located, which forms a throttle point.
 2. The filter device according to claim 1, characterized in that the control part (60) is disposed in the central longitudinal area or in the vicinity of the central longitudinal area of the tube (49).
 3. The filter device according to claim 1, characterized in that the filter element (17) can be fastened via at least one end cap (19) on an element seat (15) of the filter housing (1), and in that the tube (49) is mounted on the filter housing (1) inside the element seat (15) and extends coaxially to the longitudinal axis of the filter element (17) located in the functional position through its end cap (19) fastened to the element seat (15) and through the filter cavity (30).
 4. The filter device according to claim 1, characterized in that the external diameter and the internal diameter of the tube (49) have a stepped design, and in that the tube (49) abuts the element seat (15) by means of the longitudinal section of the larger external diameter and of the larger internal diameter, and in that the control part (60) having the through-hole (61) forms the transition between the larger internal diameter and the smaller internal diameter of the tube (49).
 5. The filter device according to claim 1, characterized in that the top end cap (51) of the filter element (17) has a tube connection (71) projecting into the inner filter cavity (25), through which the top end area of the tube (49) extends in the functional position of the filter element (17).
 6. The filter device according to claim 1, characterized in that inside the tube connection (71) of the top end cap (53) a sealing packing (55) is provided, which is penetrated in the functional position by the tube (49) and forms a sealing connection with said tube, which sealing connection seals the inner filter cavity (25) relative to the housing inner side.
 7. The filter device according to claim 1, characterized in that a fluid path (33) leading from the unfiltered side (27) to the tank return connection (13) and a blocking device (31) are provided in the filter housing (1), which blocking device blocks this fluid path (33) when a filter element (17) is inserted into the housing (1) and unblocks said fluid path (33) when the filter element (17) is removed.
 8. The filter device according to claim 1, characterized in that the blocking device has an annular body (31), which projects at the bottom end cap (19) of the filter element (17) and surrounds on this end cap the outlet aperture (29) from the filter cavity (25) forming the filtered side, which annular body (31) engages in a sealing manner in an annular gap (33) when the filter element (17) is inserted, said annular gap being formed on the element seat (15) of the housing (1) and being in fluid connection with the tank return connection (13).
 9. The filter device according to claim 1, characterized in that the annular gap (33), into which the annular body (31) of the inserted filter element (17) forming the blocking device penetrates, is delimited on the inside by an annular rib (37) of the element seat (15) surrounding the tubular body (43) at a radial distance and on the outside by a tube connection (35) projecting from the element seat (15), the outer side of which abuts the unfiltered side (27) of the housing (1) so that, when the filter element (17) is removed, the passage from the unfiltered side (27) to the fluid outlet (9) is unblocked for fluid overflowing the tube connection (35).
 10. The filter device according to claim 1, characterized in that the seal between the annular body (31) and the annular gap (33) is formed by at least one sealing element (39) provided on the outer side and/or the inner side of the annular body (31), and/or at least one sealing element (41) provided on the annular rib (37) and/or the inner side of the tube connection (35).
 11. The filter device according to claim 1, characterized in that a barrier device (43) is formed in the filter housing (1) between the fluid outlet (9) and the filtered side (25) of the filter element (17), which barrier device allows an influx of fluid to the fluid outlet (9) only upon reaching a predetermined filling level in the housing (1) by means of an overflowing of the barrier device (43).
 12. The filter device according to claim 1, characterized in that the barrier device has a tubular body (43), which projects from the element seat (15) into the inner cavity (25) of the inserted filter element (17) up to the predetermined filling level height and is connected inside the element seat (15) to the fluid outlet (9).
 13. A filter element for use in a filter device according to claim 1, which has a filter medium (30), through which fluid to be cleaned in the filtration operation can flow, which surrounds an inner filter cavity (25), and with an end cap (53) assigned in the functional position to the top end of the filter housing (1), characterized in that this end cap (53) has a tube connection (71) extending axially into the inner filter cavity (25), and in that inside said tube connection a sealing packing (55) is provided which, together with an equalizing tube (49) of the filter housing (1) penetrating said sealing packing, seals the inner filter cavity (25) relative to the surrounding housing interior. 